Fire detection systems are generally known. Such systems typically include a number of fire detectors distributed throughout a protected space and each connected to a control panel.
The connection between the fire detectors and control panel may be either wired or wireless. Wired systems are expensive to install, but are more failsafe. In the case of a wired system, power may be provided through the wires. Testing of each unit may also be accomplished through the interconnecting wires.
Conversely, wireless systems are cheaper, at least for the point of view that the fire sensors do not require the installation of wiring. Such sensors are typically battery powered and communicate using a low power radio transmitter.
Because of the reliance upon batteries; the transmitters of wireless fire detectors are typically constructed to cycle between a low power state and a higher power state where the transmitter transmits a status signal. In order to accommodate large numbers of sensors, the transmitter of such sensor sometimes operate under a time division multiple access (TDMA) format where each transmitter is assigned to operate on a specific slot of a TDMA channel.
In order to reduce power consumption as much as possible, the time slots are made as short as possible in order to reduce transmitter on-time. Because of the narrow time slots, synchronization of transmitters is important in order to ensure the reliable exchange of information. However, in order to maintain synchronization, an accurate time base is needed within each sensor. Because of the importance of fire detectors, a need exists for more flexible methods of synchronizing such fire detectors.